Sewage Projects in Yokohama City

A. Case Study Overview

1.  事業名/ Activity/ Project Title:
Sewage Projects in Yokohama City
2.  テーマ/Themes:
Climate Change, Disaster, Infrastructure, SDGs
3.  要旨/Summary:  

Through its sewage projects, the City of Yokohama is working to improve the water environment and reduce flood damage, thereby ensuring that the citizens of Yokohama can continue to lead their lives in safety and comfort. We are also working to take advantage of the sewage system’s resources to save energy and introduce renewable energy.

4.  セクター/Sector:
City : Yokohama Environmental Planning Bureau
5.  実施期間/Implementation Period:
Since 1962
6. 実施場所/Project Site :
Within Yokohama City
7.  関係機関/Stakeholders&Partners:

B. Objective:

8.  目的/Objectives:
(1) Ensure a sanitary living environment.
(2) Improve the water environment
(3) Reduce flood damage
(4) Promote the reuse of resources

C. Activities

9.   活動プロセス/Activities:
  • Sewage treatment
    In order to ensure safe and secure living conditions and a sanitary water environment, we treat sewage sludge by properly maintaining and operating sewage pipes, pumping stations, water reclamation centers, and sewage recycling centers. Nearly 100% of the city’s approximately 3.7 million citizens have access to sewer service.
  • Flood control measures
    To reduce flood damage, in addition to maintaining storm drains, storm water retention facilities are being developed in the pump drainage area.
  • Centralized treatment and reuse of sewage sludge
    Aside from collecting and efficiently treating the sludge discharged during the sewage treatment process, we are also striving to make effective use of renewable resources, such as sludge incineration ash and digester gas.

D. Challenges and solutions:

10.  課題/Challenges and solutions:

In light of the upcoming redevelopment period for the city’s sewage facilities, there is a need to step up the stock management of existing facilities.

In addition, in order to cope with increasingly intense downpours, we must also implement measures to deal with flooding. This will involve a perspective of adapting to the effects of climate change, such as promoting the use of green infrastructure.

E. Outcomes and Impacts:


As a result of intensive sewer development since the 1970s, Yokohama City’s sewer coverage rate has reached almost 100%. Today, it provides round-the-clock maintenance and management of sewer facilities, including 11 water reclamation centers, two sludge recycling centers, and approximately 11,900 kilometers of sewer pipes in order to provide sewer services to approximately 3.7 million residents.

In addition, as a result of the focused construction of facilities in areas that had a high risk of flooding, flood damage has been markedly reduced relatively to before the work.

F. Budget:

12. 予算/Budget:

252.4 billion JPY (FY 2020)

13. 財源/Source:
Sewer charges, general funds, state subsidies, corporate bonds, etc.